New England Pellet Stove keeps "CLICKING"

Hi everyone, I just purchased a new England pellet stove 2 months ago. (25-pv something like that) heats 1500 sq ft. I have used it for two weeks. First week, loved it, this past week.....it makes a clicking sound like the sound of metal expanding, not a steady or timed "clicking", it is constant though.....driving me nuts. I've tried to call the manufacturer, busy all day long. I've cleaned it daily...no "clinkers", bolts, screws all tight, I can't figure it out and I can't take it any longer. Any suggestions would be greatly appreciated. Thanks in advance.